ZeMac® E-60P powder and ZeMac® Extend master batch pellets are very efficient as a chain extenders to increase relative viscosity and mechanical properties such as tensile strength, elongation and modulus, flex strength and modulus, impact strength especially at low temperature, HDT, and bending strength of polymers containing hydroxyl or amine end groups such as polyamides, PBT, and other engineering polymers, while at the same time acting as a Branching Agent to provide shear thinning at high shear for improved processing of these plastics. These products are used to upgrade recycled nylon, virgin nylon, other polyamides and engineering plastics. When used to upgrade recycled engineering plastics, these products are referred to as recycling agents.